The motor cortex and basal ganglia play an important role in the regulation of behavior. Clinical and experimental observations on disease or damage to the motor cortex and basal ganglia have described, among other deficits, marked impairments in the initiation of movement and in the ability to perform complex cognitive and motor tasks. Recent electrophysiological studies by the applicant have revealed a topographic axio-distal distribution of motor cortex outputs to the caudate nucleus. Current experiments will determine how this axio-distal sorting is mirrored at the level of the caudate output to the globus pallidus. The electrophysiological experiments proposed will investigate the manner in which the basal ganglionic output to the thalamus interacts with the topographic projections from the deep cerebellar nuclei to the thalamus. These experiments will provide valuable information on the organization of the neurological substrates involved in the modulation of axial and distal musculatures via the thalamocortical pathway in intact animals and in animals with brain lesions. These studies should lead to a better understanding of the normal function of and the effects of lesions on brain systems involved in the initiation of movement. The results from these experiments will hopefully suggest new procedures for alleviating the disorders produced by disease or damage to these brain systems.